When switched "On", Remember and Repeat replicates the standard classroom spelling strategy Read Cover Write Check. A student types a word, it disappears and they immediately type it again from memory, benefitting from the extra repetition.
This is how you find the option in the Settings menu:
It is recommended that this feature is used when a student reaches words that they are finding particularly difficult to spell.
When Remember and repeat is switched on, an icon (RR) will appear on the keyboard screen.